The Computational Dictionary, described in this paper, is structured on a knowledge base. The semantic features of each word, in a relevant grammatical category, can be determined through a hierarchical tree structure. Semantic knowledge of verbs is represented using predicate calculus definitions. This allows each expression, e.g. sentence or command, to be tested in order to determine whether it is meaningful and, if meaningful, what its meaning is or indeed whether it is ambiguous.

A significant factor in air accidents is "pilot error". Included in this category are errors in natural language communication between the pilot and air traffic control (ATC); errors possibly compounded by the use of English as a standard language for such communication. We concentrate on the likelihood of misunderstanding created by ambiguities in these messages. Often only a few seconds exist between the receipt of an ambiguous message and the subsequent incorrect action (potentially) leading to a fatal accident. We consider the feasibility of filtering each spoken message through an "intelligent computer interface", testing for ambiguities and only transmitting those messages which are clear and unambiguous. Unclear, ambiguous messages should be "authenticated" before transmission. The procedures for computer analysis would require not only sensitive speech recognition equipment but also complex software performing sophisticated linguistic analysis at the phonetic, syntactic, semantic and pragmatic levels. Analysis must also take place in "real time" so that both pilot and controller can receive warning that ambiguities exist in the last communication and corrective action taken in the short time available. Consideration is also given to extending the system from the monolingual to multilingual level allowing pilot and controller each to think and speak in his own native tongue. The sophisticated language analysis is being extended to allow for appropriate disambiguated, bilingual machine translation.